1. Field of the Invention
This invention relates to a liquid jet recording head, and more particularly to a recording head for generation of small droplets of a liquid for recording to be used in a liquid jet recording system in which recording is performed by generating small droplets of a liquid for recording such as ink, etc., and attaching them onto a recording medium such as paper.
2. Related Background Art
The liquid jet recording system which performs recording by generating small droplets of a liquid for recording such as ink, etc., and attaching them onto a recording medium such as paper is attracting attention as a recording system which generates very little noise during recording, enables high speed recording and requires no special treatment such as fixing to perform recording on a plain paper, and thus various types of this system have been actively studied.
The recording head portion of the recording device to be used in the liquid jet recording system generally consists of an orifice for discharging a liquid for recording (liquid discharging outlet), a liquid passage connected to said orifice and having a portion at which energy for discharging a recording liquid acts on the recording liquid and a liquid chamber for storing a recording liquid to be fed into said liquid passage.
The energy for discharging the recording liquid during recording is generated in most cases by means of a discharge energy generating element of various types such as heat generating elements, piezoelectric elements, etc. which is arranged at a predetermined position and constitutes a part of the liquid passage where the discharging energy is permitted to act on the recording liquid (energizing portion).
As a method for preparing a liquid jet recording head with such a constitution, there have been known, for example, methods comprising the steps of forming fine grooves on a flat plate of glass, metal, etc. by cutting or etching and then bonding another appropriate plate onto the flat plate having such grooves formed thereon to thereby form liquid passages, or methods comprising the steps of forming groove walls of a cured photosensitive resin by photolithography on a substrate having a discharging energy generating element arranged thereon to provide grooves for the liquid passages on the substrate and then bonding another flat plate (covering) onto the grooved plate thus formed to thereby form liquid passages (for example, Japanese Laid-open Patent Publication No. 43876/1972).
Among these methods for preparation of a liquid jet recording head, the latter group of methods employing a photosensitive resin are more advantageous than the former group of methods since liquid passages can be finely manufactured with higher precision and yield and liquid jet recording heads can be obtained with better quality and lower cost due to mass-producibility.
As a photosensitive resin to be used in preparation of such recording heads, there are employed those to be used for pattern formation in printing plates or print wirings or those known as the photocurable coating materials or adhesives to be used for glass, metal, ceramics, etc. Also, in aspect of work efficiency, dry film type resins have been primarily utilized.
In order to give excellent characteristics such as high recording characteristic, durability, reliability, etc. to a recording head employing a cured film of a photosensitive resin, the photosensitive resin used for the recording head is required to have the characteristics as follows:
(1) particularly, excellent adhesion as a cured film to a substrate;
(2) excellent mechanical strength and durability, etc., when cured; and
(3) excellent sensitivity and resolution upon patterning by use of pattern exposure technique.
However, under the present situation, none of the photosensitive resins to be used for formation of a liquid jet recording head hitherto known in the art satisfy all of the above requisite characteristics as mentioned above.
To describe in more detail, those employed for pattern formation in printing plates, print wirings, etc., as a photosensitive resin for recording head, are inferior in adhesion or close contact with glass, ceramics, plastic films, etc. to be used as a substrate although they are excellent in sensitivity and resolution, and insufficient in mechanical strength and durability when cured. For this reason, there is involved the drawback that, at the stage of preparation of recording heads or in the course of usage, deformation, peel-off from the substrate or damages of the resin cured film are liable to occur, which may cause marked impairment of reliability of the recording head such as lowering in recording characteristics by impeding the flow of a liquid for recording in the liquid passages or making the liquid droplet discharging direction unstable.
On the other hand, those which are known as photocurable type coating materials or adhesives to be used for glass, metals, ceramics, etc., although having advantages of excellent close contact or adhesiveness with the substrate composed of these materials as well as satisfactory mechanical strength and durability after cured, are inferior in sensitivity and resolution and therefore require an exposure device of higher intensity or an exposure operation for longer time. Further, their inherent characteristics cannot afford a precise and high density pattern with good resolution, whereby there is involved the problem that it is not suitable for a recording head for which minute precise working is particularly required.